U.S. patent number 5,361,893 [Application Number 08/153,979] was granted by the patent office on 1994-11-08 for high friction plastic conveyor belts having modular links formed by two integrated plastic materials.
This patent grant is currently assigned to The Laitram Corporation. Invention is credited to John J. Carbone, Robert S. Lapeyre.
United States Patent |
5,361,893 |
Lapeyre , et al. |
November 8, 1994 |
High friction plastic conveyor belts having modular links formed by
two integrated plastic materials
Abstract
A plastic conveyor belt system provides high frictional surface
contact between the conveyor work surface and the load carried by
the conveyor. This is achieved by modular belt links integrally
formed of two diverse plastic materials such as a low friction
polypropylene and a high friction elastomer thermoplastic rubber.
Typically a belt modular link having a planar load support area
disposed in its lower forming mold piece with an upper mold piece
removed to expose the planar area. Then a further mold piece is
mated with the lower mold piece to integrally join by thermal
bonding the two diverse materials producing on the planar link load
bearing surface area an elastomer strip with an outer frictionally
textured surface for encountering the belt load.
Inventors: |
Lapeyre; Robert S. (New
Orleans, LA), Carbone; John J. (Metairie, LA) |
Assignee: |
The Laitram Corporation (New
Orleans, LA)
|
Family
ID: |
22549520 |
Appl.
No.: |
08/153,979 |
Filed: |
November 18, 1993 |
Current U.S.
Class: |
198/853; 198/851;
198/690.2 |
Current CPC
Class: |
B65G
17/08 (20130101); B65G 17/34 (20130101); B65G
2201/02 (20130101); B65G 2201/0211 (20130101); B65G
2207/30 (20130101) |
Current International
Class: |
B65G
17/32 (20060101); B65G 17/08 (20060101); B65G
17/34 (20060101); B65G 17/06 (20060101); B65G
017/06 () |
Field of
Search: |
;198/849-853,688.1,690.2
;425/406,407,408,384,390,412 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
0162413 |
|
Sep 1983 |
|
JP |
|
2164313 |
|
Mar 1986 |
|
GB |
|
2185725 |
|
Jul 1987 |
|
GB |
|
Primary Examiner: Bidwell; James R.
Attorney, Agent or Firm: Brown; Laurence R.
Claims
We claim:
1. A modular link plastic conveyor belt adapted to convey loads up
and down inclined surfaces comprising in combination,
a plurality of plastic modular link bodies coupled end-to-end to
form a conveyor belt, each said link body being formed of a hard
wear resistant plastic material having a low coefficient of
friction shaped to provide a rigid high strength conveyor link base
structure, low-friction belt-supporting load-bearing wear strip
surfaces positioned on an outer belt surface in frictional
engagement with link bodies moving about a conveyor belt path, each
said link body forming pivot aperture means near two opposite ends
coupling the bodies pivotably together end-to-end with pivot rods
extending through the apertures, thereby to establish high
longitudinal belt strength when so coupled end-to-end in a belt of
a predeterminable fixed length and presenting an outer low friction
contact surface in sliding contact with said belt supporting wear
strip surfaces during transport of said conveyor belt, said bodies
being shaped to present an outer load carrying surface having a
load bearing area presented for frictional contact with a load
being carried by the conveyor belt; and
a load transport body of a high friction material for presenting a
high friction outermost textured contact surface between said load
carrying surface and a load carried by said conveyor belt, said
high friction material being thermally bonded with said load
carrying surface to substantially cover said load bearing area and
provide with at least some of said link bodies a unitary integral
modular conveyor belt link with a high friction load carrying
surface.
2. The conveyor belt system of claim 1 further comprising a
conveyor belt having a width of a plurality of lanes of modules
bricklayered into a belt configuration including separate lanes of
modules formed of low friction material exclusive of said high
friction material thereby forming said wear strip surfaces for
frictional contact with the low friction load bearing surfaces in
said separate lanes of the belt.
3. The modular link of claim 1 wherein the load transport body
presents a textured surface pattern extending outwardly from the
surface of the high friction material in a set of interconnected
ridges that conform resiliently to load bodies in contact
therewith.
4. The modular link belt of claim 1, wherein the low friction base
body has interdigitatable link end fingers extending from the base
body at opposite link ends defining said aperture means for
receiving pivot pins wherein the surface of the high friction
material is shaped to overlap onto the interdigitatable
fingers.
5. The modular link belt of claim 1 further comprising sprocket
drive means for transporting said belt wherein the body of low
friction material is shaped to form sprocket drive engaging
structure for low friction contact transport drive of the conveyor
belt from a sprocket drive gear.
6. The modular link belt of claim 1 wherein the low friction link
bodies present a substantially continuous longitudinal aperture
free planar load bearing area surface of substantially constant
width, and the load carrying surface forms a mating substantially
planar continuous longitudinal surface bonded to the load bearing
area surface of the plastic body.
7. The conveyor belt system defined in claim 1 wherein the plastic
bodies have sprocket drive tooth structure for engaging sprocket
wheel drive teeth, said system further comprising a sprocket drive
system having sprocket wheel teeth engaging the low friction
plastic sprocket drive tooth structure of the modular link for
transport of the conveyor belt.
8. The conveyor belt system defined in claim 1 further comprising a
conveyor belt system having sets of end-to-end coupled said modular
links disposed in side by side lanes to form a multiple lane
conveyor belt of a width determined by the side-by-side lanes.
9. The conveyor belt system defined in claim 8 wherein the modular
links in at least one lane of said conveyor belt consist of said
plastic bodies exclusive of said high friction surface whereby the
links present said load bearing area with a low friction surface,
and wherein the conveyor belt links are connected into an endless
loop with a non-loadbearing return path, and further comprising at
least one said wear strip surface located in the return path to
contact the low friction plastic surface of bodies exclusive of
said high friction surface in a belt supporting relationship.
10. A modular conveyor belt link for carrying loads up and down
inclined surfaces molded into an integral body from two diverse
thermoplastic materials by a first molding step producing and
retaining in a first mold piece of a two piece mold a conveyor link
belt module of low friction rigid plastic material containing a
load supporting surface and by a second molding step
thermoplastically molding a body of high friction resilient
material to said load supporting surface of the link with a third
mold piece thereby to thermally bond the two materials together
into an integral new modular link with a high friction load bearing
surface for moving loads up and down inclined surfaces.
11. The method of making two different plastic conveyor chain
modular links of different characteristics with a common basic mold
comprising the steps of: molding a hard, low friction plastic
material between two mold cavities comprising a basic mold for
retaining the molded modular link and a removable mold for forming
the plastic molded modular link to form a first modular link of a
base structure of a low friction rigid plastic material which
presents a load bearing surface, removing the removable mold piece
from the basic mold which retains the molded plastic modular link,
mating a third mold piece with the basic mold to thermally bond a
further body of high friction thermoplastic rubber material on the
load bearing surface of the first module thereby forming in said
mated basic and third mold pieces an integral elastomeric
conveyance surface configuration superimposed integrally on the
molded modular link by thermally bonding the elastomeric
configuration to the plastic load bearing surface of the first
molded module to produce the second module of different
characteristics.
12. An integrally bonded modular link for a plastic conveyor belt
system formed in part of a hard wear resistant plastic material
providing a low coefficient of friction disposed on an inwardly
disposed belt surface thereof and in part of a high friction
resilient contact surface material having ridges outwardly
extending from an outwardly disposed belt surface for conforming
resiliently with load bodies in contact therewith.
13. A link as defined in claim 12 defining at two link ends with
said hard plastic material a set of interdigited fingers having a
set of pivot pin receiving apertures axially aligned therein
disposed between two substantially parallel link sides, wherein
said resilient surface material extends to cover said interdigited
fingers thereby to produce a substantially continuous longitudinal
conveyor load carrying surface along the length of a conveyor belt
formed from such links.
Description
TECHNICAL FIELD
This invention relates to plastic modular conveyor belts and more
particularly it relates to conveyor belts with plastic modular
links integrally formed of two different plastic or rubber
materials.
BACKGROUND ART
Modular plastic links for conveyors are typically formed of
polyethylene, polypropylene or acetal, which are hard, wear
resistant plastics having a low coefficient of friction ideal for
pivoting the links and frictional contact with wear strip surfaces.
These plastics also provide a high tensile strength along the belt
for conveying heavy loads and ideal chemical and biological
inactivity for use of the belts in sanitary and chemical
environments. However, the low friction characteristics of the
plastics do not form an ideal belt-to-load surface for carrying
loads up and down inclines.
In the prior art, fabric and rubber-like belts have been used
extensively to increase the friction of the carrying surface of the
belts. However, these belts have certain shortcomings. Because
significant friction between a fabric belt and its driving drum is
required to effectively drive the belt, fabric belts are maintained
in high tension, even while not operating. The high tension
stretches the belt and strains the conveyor frame and tensioner.
Another shortcoming with fabric belts is that they are not
positively tracked, making them susceptible to edge damage as the
untracked belt wanders from side to side. Repair is another problem
with fabric belts. Removing worn sections, inserting splices,
determining the correct length, and reinstalling and retensioning
the repaired belt can be difficult. Furthermore, the roller
carryways used with fabric belts are noisy.
It is therefore a primary object of this invention to resolve these
problems by manufacture of high friction link belt modules and to
provide improved high friction conveyor belts and conveyor
systems.
DISCLOSURE OF THE INVENTION
In accordance with this invention modular plastic link belts are
made with high friction surfaces by providing integral modular
links bonding together two different plastic or rubber materials.
One material, typically an elastomer such as a thermoplastic rubber
is disposed on the load transport surface to provide a high
friction transport surface. The other material, typically acetal,
polypropylene or polyethylene, forms a module with link ends for
receiving pivot rods for coupling modules together end-to-end in a
low friction, high strength, rigid belt assembly of fixed length
for driving by sprocket wheel assemblies. The materials are
thermally bonded by molding to form unitary modular link elements
with a high friction load transport surface.
Further objects, features and advantages of the invention will be
found throughout the following description, drawings and
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings, wherein like reference characters
refer to similar features throughout the various views to
facilitate comparison:
FIG. 1 is an exploded perspective sketch of a modular belt link
afforded by this invention having an integral body formed of two
different materials, respectively characterized by low and high
coefficients of friction;
FIG. 2 is a plan view of a high friction textured overlay pattern
for forming a load carrying surface of a conveyor belt;
FIGS. 3 to 5 are respectively section sketches of a lower and two
alternating upper mold pieces employed to integrally mold a modular
belt link from two different materials in accordance with this
invention;
FIG. 6 is a side view sketch, partly in section, showing a fragment
of a modular link belt with modular links pivoted together;
FIG. 7 is a fragmentary side view sketch of a sprocket driven
conveyor belt system embodying the invention; and
FIG. 8 is a cross-sectional elevational view of a conveyor
embodying the invention showing an upper carryway and a lower
returnway with the belt supported by wear strips in contact with
low friction surface portions.
THE PREFERRED EMBODIMENTS
The modular link of FIG. 1 has the anti-skid conveyor load carrying
surface member 11 and the link end carrying base member 12 formed
of two separate materials bonded together integrally at the top
surface interface 15. For functionally adapting the modular link
element to resolve the aforesaid problems of the prior art, the
base element 12 is formed of a strong, hard plastic material having
a low coefficient of friction, typically acetal, polypropylene or
polyethylene, and the surface member 11 is of an elastomer,
typically a thermoplastic rubber having a high coefficient of
friction. The elements are bonded together at the interface surface
15 preferably by thermal injection molding.
The surface friction member 11 in one embodiment is textured to
present an anti-slip high friction load carrying surface having
diamond shaped ridges 16 extending upwardly from an unapertured
carrying surface strip 17. When the friction member 11 is
superimposed on the flat-top surface 15 of the base elements 12
connected pivotably end to end, there will be a gap between the
strips 17 extending over the link ends 18 of the base elements
12.
However, the textured surface of the modified friction member 11'
in FIG. 2 provides mating link end members 19 that will overlap and
interdigitate with the link ends 18 to form a substantially
continuous load bearing anti-slip surface over the length of the
belt.
It should be appreciated that, although the embodiments shown have
flat-top surfaces, it is also possible to have perforated or
otherwise open-area belt modules for drainage or air flow.
The integral modular lines are molded in the manner represented by
the mold pieces shown in FIGS. 3, 4 and 5. Thus the base member 12
resides in the lower mold half 21 after the upper die half 22 has
been removed. Then the alternating die half 23 is mated with lower
die 21 to thermally bond the surface member 11 to the flat upper
surface of link 12, preferably by injection molding.
Belt systems constructed with interconnected finished modular links
25, 26, as shown in FIG. 6, representing a fragmental portion of a
pivoted link conveyor belt 24 in FIG. 7, thus present an anti-slip
upper load bearing transport surface 27 formed of the high friction
material, and a lower link base of stronger and longer wearing hard
plastic having lower friction. The low friction material of the
base member 12 at the pivot zones 29 is crucial, as is the low
friction interface at the wear plates 31 of the conveyor belt array
of FIG. 7. Also the low friction interface of the sprocket teeth 32
with the hard plastic low friction material is crucial to belt wear
and permits the use of more positive sprocket drive to replace
rollers that were used heretofore with fabric belts necessary to
provide high friction load carrying interfaces.
Since the softer resilient elastomeric material of the antislip
surface 27 is more subject to wear, the lowermost return path of
the link belt is passed over small diameter rollers 33 in
embodiments where there must be contact with the high friction
material. The resulting conveyor link belt system is not
compromised in terms of pulling capacity or tensile strength with
the construction of links as taught by this invention.
Another advantage of the modularity of the invention is that
various patterns of high-friction surfaces can be arranged in
constructing a conveyor belt. For example, as shown in FIG. 8, belt
modules 40 lacking high-friction conveying surfaces can be
bricklayed with modules 41 having high-friction surfaces in a
loadbearing surface pattern characterized by low-friction bands 42
along the edges 43 or internal portions 44 of the belt. Stationary
wearstrips 45 or shoes 46, rather than the moving roller 33 of FIG.
7, can be positioned along the return path 47 in line with the
low-friction bands 42 to minimize friction and wear. Equivalently,
modules can be molded with longitudinal gaps between high-friction
surface material so that a conveyor belt having lowfriction
longitudinal bands along the load-bearing side can be
assembled.
A further significant advantage of this invention is the ease of
repair of modular link belts simply by module replacement, which
replaces the prior art practice of making of incompatible joints to
connect ends of fabric belts together. The design of proper link
belts is facilitated by the link construction, and the hard plastic
is not subject to any extensive stretching or fatigue.
It is noted that with the shown construction the high friction
material is not required to bend as it articulates about the
sprocket assembly 36 of FIG. 7. Thus this system is superior to a
drum drive fabric belt system, or any system superimposing a
non-modular surface material along the length of a modular belt
system.
This invention therefore provides in one embodiment a modular link
for a plastic conveyor belt adapted to convey loads up and down
inclined surfaces by way of a thermally bonded surface member 11
affixed unitarily to a basic modular link to serve as a high
friction load transport body. Thus, surface member 11 is made of
high friction elastomeric material that thermally bonds to form a
unitary modular link with the basic plastic modular link body of
base member 12. Thus a basic modular link formed of hard, wear
resistant plastic material having a low coefficient of friction
with a shape presenting a load carrying surface with a
substantially planar load bearing area 15 is converted into a high
friction modular link capable of carrying loads up and down an
inclined surface. The hard plastic region serving as interface
surface 15 forms a thermal bond with dissimilar compressible
thermoplastic frictional materials to produce a unitary modular
conveyor belt link of different load bearing characteristics. These
links when coupled end-to-end form a belt of predeterminable fixed
length that retains high longitudinal belt strength and low
friction contact surfaces for belt transport bearing surfaces and
pivot joints. Improved conveyor belt systems using these modules
function over a wide range of loading requirements including
transport up and down inclined surfaces.
The high friction load transport body encompasses substantially the
entire load bearing area of the modular links to produce maximum
load support, friction and bonding strength. A textured surface
(FIGS. 1, 2) extending outwardly from the surface of the high
friction material in a set of interconnected ridges will conform
resiliently to load bodies in contact therewith for additional
functional advantage in conveying different types of loads. The
load transport body in the embodiment of FIG. 2 has
interdigitatable link end fingers extending from the main body of
high friction material to overlap the link end fingers 18 on the
basic module (FIG. 1).
The high friction material does not interfere with the favorable
drive characteristics of the low friction hard plastic of the basic
modular link structure, and therefore serves advantageously with
sprocket drive gear transport of the belt. That is, there is no
particular forces on the large thermoplastic bonded area that tends
to disrupt the unity of the load bearing modular unit, since the
load offers basically a downward compression with little shear
force that would tend to cause catastrophic failure. Furthermore,
the placement of the two diverse materials in the modular link
conveyor belts of this invention is such that the hard plastic
material is used to contact frictionally wear strips with minimal
friction.
In particular, this invention provides two compatible modular links
which may be bricklayed in a conveyor belt of desired width to
provide separate lanes of either modules with high friction load
bearing surfaces to transport loads or with low friction long
lasting plastic surfaces that mate with wear strips, typically
installed on belt return paths, which would otherwise interfere
with high friction surfaces on the load bearing surfaces unitary
modules formed from diverse materials supplied by this
invention.
Having therefore advanced the state of the art, those novel
features believed descriptive of the nature and spirit of the
invention are defined with particularity in the following
claims.
* * * * *